1. Field of the Invention
The present invention relates to a vibrator for an angular rate sensor used for detecting a turning angular rate in a turning system, a vibratory gyroscope using the vibrator, a linear accelerometer and a method for detecting a turning angular rate.
2. Description of the Related Art
Up to now, as an angular rate sensor used for detecting a turning angular rate in a turning system, a vibratory gyroscope using a piezoelectric member has been used for detecting position of an aircraft, a ship, or a space satellite. Recently, it is used in a car-navigation system, a movement detecting mechanism in a VTR or a still camera in the field of public livelihood.
Such a vibratory gyroscope utilizes the concept that, when an angular rate is applied to a vibrating object, Coriolis force is generated in the direction perpendicular to the vibratory direction. Its mechanism is analyzed by using a dynamic model (for example, "Handbook of Elastic Wave Device Technologies" (Danseiha-Sosi Gijutsu Handbook) issued by Ohm, Inc., pp.491 to 497). Various kinds of piezoelectric vibratory gyroscopes have been proposed up to now. For example, a Sperry tuning-fork gyroscope, a Watson tuning-fork gyroscope, a regular-triangle prism-shaped tuning-piece gyroscope, a cylindrical tuning-piece gyroscope are known as a piezoelectric vibratory gyroscope.
This type of vibratory gyroscope utilizing a disk-shaped vibrator was disclosed, for example, in U.S. Pat. No. 5,540,094, in which driving vibration, for example with four nodes, was excited in the disk-shaped vibrator, the vibrator was then turned around an axis perpendicular to the disk-shaped vibrator to induce detection vibration, whose amplitude was detected. Such induced detection vibration also comprises four nodes within.